Protection of pharmaceutical, nutritional and nutraceutical dosage forms from environmental moisture, especially at elevated temperatures is important when the active material is adversely affected by the presence of moisture and/or heat. The negative effects of moisture may occur during common production processes such as processes that involve wet granulation and/or coating. Alternatively, the moisture may damage the active material during storage and negatively affect the shelf life of a final product. Common approaches aimed to limit the damage to the active material, include packaging of the dosage forms containing the moisture sensitive active material in different packaging elements, such as microcapsules, tablets, capsules and the like. However, especially in places where climate is very humid, the special packaging does not provide a complete moisture protection because of the moisture captured inside the above mentioned packaging. Another way to prevent or diminish the damage that may be caused by moisture and to reduce the need for special packaging is to coat the solid dosage forms with materials which have moisture barrier properties. Such materials have essentially a low water vapour permeation (WVP) or a low water vapor transition rate (WVTR). These coatings usually do not affect the basic properties of the dosage forms such as the disintegration time and the release profile of the active material. Examples of moisture sensitive drugs include atorvastatin, ranitidine, temazepam, most vitamins, numerous herbals, unsaturated fatty acids and probiotic bacteria. The damage that may occur due to moisture may include, for example, degradation of active material by hydrolysis, destruction of probiotic bacteria or significant reduction in CFU (colony forming unites) value, changes in the appearance of the dosage form on storage, changes in the disintegration and/or dissolution times of the dosage form. Moisture barrier coatings are thus applied to protect the dosage form from such damages.
In order to achieve a moisture barrier coating, usually a hydrophobic water insoluble polymer is used. The polymers generally employed for this purpose are polyvinyl acetate, zein, shellac, cellulose acetate phthalate (CAP), EUDRAGIT® E 100 which is a cationic copolymer based on dimethylaminoethyl methacrylate, butyl methacrylate, and methyl methacrylate with a ratio of 2:1:1, ethylcellulose (EC) and the like. Such polymers, however, prolong the disintegration of the dosage form in the body after administration and thus delay the release of active materials or probiotic bacteria. Likewise, coating with these polymers necessitates the involvement of use of organic solvent which is not desired because such a process enforces additional expenses relating to air conditioning equipment, anti-explosion provisions, and the like to safely handle such materials. Another way to achieve a moisture barrier coating is a combination of a water soluble polymer with lipophilic substances. The hydrophobic or lipophilic substances particles will be embedded in water soluble film after coating or film formation. Although the presence of lipophilic substance particles in the film may reduce the water vapour transition, they cannot cover all the area of the film, and thus water vapour can still easily penetrate through the spaces between the particles.